What can cause the water in the tub to back up .I have tried different plumbing materials such as Draino. How can I clear the lines so the water can star drain by its self.

Tahccd23 - IF you have tried all this ,then you have a prety good blockage,most likely. One thing that really clogs up a sink or tub drain is HAIR hung up just inside the drain , For a start lets take the metal piece on the drain and use a soft type clothes hanger and put it down the drain and then pull it back out to see what we have on the wire

Tell me dose the sink drain work and drain good ? If it does it is probably plugged up then before it meets the drain from the sink. Most of the time the sink and tub drains come togreather before going into the toilet drain, which goes into the main drain under the house
Another thing you can try is to take the two screws out of the over flow tube and then raise it up just a little and run some water in the tub and then release the water and see how it drains then . Some times it is not adjusted right and does not open the drain up fully , maybe it only has a very small oppening to let water out very slow. TRY tyhis and then get back on here and we will try harder stuff ( HOPELY NOT ) Good luck & GOD BLESS ;;; F.B.E.

I recently bought a thing at a home store that looks like a 2' long narrow plastic strip with a small barb every inch. You stick it down the drain and pull it back. It does a great job on hair, I now use it prophylactically. You can also try my home remedy. Mix 1/2 cup of table salt with equal amount of baking soda and ump down the offending drain, add a cup of vinegar. The next day flush with a big bucket of really hot water.